This invention relates to the field of medical devices, and more particularly to a catheter having a shaft with a minor transverse dimension and a major transverse dimension.
In percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter is advanced until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire, positioned within an inner lumen of an dilatation catheter, is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guidewire crosses a lesion to be dilated. Then the dilatation catheter having an inflatable balloon on the distal portion thereof is advanced into the patient""s coronary anatomy, over the previously introduced guidewire, until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with liquid one or more times to a predetermined size at relatively high pressures (e.g. greater than 8 atmospheres) so that the stenosis is compressed against the arterial wall and the wall expanded to open up the passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. Substantial, uncontrolled expansion of the balloon against the vessel wall can cause trauma to the vessel wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilation catheter can be removed therefrom.
In such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate and to strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter, and the expanded stent is left in place within the artery at the site of the dilated lesion.
One difficulty has been the use of stents at bifurcation lesions, also known as ostial lesions, in which a lesion is located in a branch vessel at the intersection of the branch vessel and the main vessel. Complicated stenting techniques are used which require multiple balloon catheters and multiple wires, and which frequently result in sub-optimal or improper stent placement due to the difficulty of precise positioning of the stent in the branched anatomy.
It would be significant advance to provide a catheter with improved ability to position the operative distal end of the catheter.
The invention is directed to a catheter including an elongated shaft having a proximal end, a distal end, at least one lumen, and at least a section with a major transverse dimension and a minor transverse dimension, such that the shaft preferentially bends in the direction of the minor transverse dimension. In one embodiment, the catheter is a balloon catheter having a balloon on a distal shaft section, and having a prosthesis mounted on the balloon. In a presently preferred embodiment, the prosthesis has a first end and a truncated second end, and is mounted on the balloon such that the truncated second end tapers in the direction of the minor transverse dimension of the shaft. In another embodiment, the catheter has an operative member, such as a drug delivery balloon, an atherectomy member, or an emitter such as a radiation, sonic, or light emitter, disposed on or within a distal shaft section, and the operative member has an operative surface facing in a direction aligned with the direction of the minor transverse dimension of the shaft. The shaft preferentially bends in the direction of the minor transverse dimension, to thereby provide improved ability to position a prosthesis or the operative surface of a catheter operative member in a desired orientation within a patient""s body lumen.
In the embodiment of the invention in which a prosthesis having a truncated end is mounted on the balloon, a variety of different prostheses may be used including stents, grafts, and the like. In a presently preferred embodiment of the invention, a balloon catheter, which in accordance with the invention has a shaft having a minor transverse dimension and a major transverse dimension, has an angulated ostial stent mounted on the balloon. The angulated ostial stent has a truncated end which is configured to align with an ostium of a branch lumen of a bifurcated body lumen. With the stent mounted on the balloon so that the truncated end tapers in the direction of the shaft minor transverse dimension, the balloon catheter will bend to thereby position the truncated end of the stent in the correct orientation or 180xc2x0 out of phase within the branch body lumen. By limiting the different possible orientations in which the stent arrives at the bifurcated lesion site, the catheter provides improved ability to correctly position the stent. By visualizing the stent, as for example by fluoroscopy of a radiopaque stent, the physician can determine if the stent is correctly positioned or is 180xc2x0 out of correct position in the branched body lumen. If the stent is 180xc2x0 out of phase with the ostium of the branched body lumen, the catheter can be torqued from outside the patient to turn the catheter balloon 180xc2x0, to thereby correctly orient the angulated ostial stent. In addition to correctly positioning angulated ostial stents in a patient""s body lumen, the catheter of the invention can be used to correctly position a variety of rotational orientation-sensitive devices such as aperture stenting devices, drug delivery devices, radiation, sonic or light delivery devices, where lesion or location specific placement is desired. For example, in one embodiment, a radiation source wire within a lumen of the catheter shaft has a radiation emitting surface facing in a direction aligned with the minor transverse dimension of the shaft, so that the radiation emitting surface faces towards the major transverse dimension of the shaft.
The terminology major transverse dimension and minor transverse dimension should be understood to mean that at least a section of the shaft extending all or part of the length of the shaft has a width in a first direction (i.e., the minor transverse dimension) which is less than a width in a second direction (i.e., the major transverse dimension), the second direction typically being perpendicular to the first direction. Thus, the aspect ratio between the minor transverse dimension and the major transverse dimension is less than one. The preferred aspect ratio between the minor transverse dimension and the major transverse dimension depends on a variety of factors including the catheter application, the nature of the material used to form the shaft, the catheter and catheter lumen dimensions, and the catheter lumen function. In one embodiment, the aspect ratio of the minor to the major transverse dimension is preferably about 1:1.5 (0.67) to about 1:4 (0.25).
The catheter shaft of the invention having a major transverse dimension and a minor transverse dimension may have a variety of suitable shapes including oblong, triangular, and dumbbell shaped transverse cross sections. Additionally, a variety of suitable catheter configurations may be used including a dual lumen shaft, and a dual member shaft having an inner and outer tubular member. In a presently preferred embodiment, the catheter is caused to passively assume the preferential bent shape when the catheter is advanced within the turns of a patient""s vasculature. However, in alternative embodiments, the catheter may be provided with a deflection mechanism such as a deflection wire which can be activated, as for example by pulling the wire, to deflect the distal end of the catheter.
The catheter of the invention provides improved positioning of angulated ostial stents and other rotational orientation specific members, due to the orientation of the stent or other member on the catheter relative to the major transverse dimension and the minor transverse dimension of the catheter shaft. These and other advantages of the invention will become more apparent from the following detailed description of the invention and the accompanying exemplary drawings.